Scattering due to irregularities on dielectric or optical fibres

The effect on mode propagation of small (with respect to wave-length) irregularities or imperfections in a dielectric waveguide is analysed. Asymptotically, for large frequencies, the power which is scattered in the form of radiation (not guided) has an ¿2 behaviour, and that scattered into the modes obeys a 1/¿2 relationship. At the frequency of paramount interest for optical communication (cutoff for TM01 mode), the radiated power is 22dB larger than the power scattered into the HE11 mode.